Generally, a power conversion device used in an uninterruptible power supply apparatus or the like includes a converter configured to convert AC power from a commercial AC power supply into DC power and an inverter configured to convert DC power into AC power with a desired frequency and a desired voltage.
For example, WO 2010/095241 (PTL 1) discloses an uninterruptible power supply apparatus constituted by a power conversion device including a three-level converter and a three-level inverter. In the power conversion device, each of the three-level converter and the three-level inverter includes a plurality of semiconductor switching elements.
In the power conversion device described above, if one of a plurality of semiconductor switching elements is damaged and short-circuited, an overcurrent or an overvoltage may occur. In PTL 1, a fuse is connected between one terminal of each semiconductor switching element and a DC bus line (DC positive bus line, DC negative bus line or DC neutral bus line). Thus, if one of the semiconductor switching elements is short-circuited, the fuse is blown to interrupt the current path, and thereby, it is possible to prevent the overcurrent or the overvoltage from occurring.